Sound insulating material and method of making the same



Dec. 15, 1964 D. CHAPMAN 3,161,258

SOUND INSULATING MATERIAL AND METHOD OF MAKING THE SAME Filed Nov. 29, 1961 2 Sheets-Sheet 1 l Il Il IN1/mmeh DAVE CHAPMAN EEE- Dec. 15, 1964 D. CHAPMAN 3,161,258

SOUND INSULATING MATERIAL AND METHOD OE MAKING THE SAME Filed Nov. 29, 1961 2 Sheets-Sheet 2 i-1 QT? llllllllll IIIIIIIIIIIII I'NVEN TOR.

" 39 DAVE CHAPMAN United States Patent O .@,iilliti SUND INSULATNG MATEl lifall METHD @F MAKHYJG T itil tishftii Dave Chapman, Chicago, lll., assigner to Moira :o indus tries, Inc., Amsterdam, NX., .a corporation of New York Filed Nov. 2i), wel, No. lfilti i7 Ciaims. (Cls 13b-33E The present invention generally relates to sound insulating materials which are non-rigid, generally sheetlike in construction, and which may be used for high transmission loss movable partitions. The basic principle upon which such materials operate to provide a barrier to sound waves is disclosed in my co-pending application, Serial No. 124,275, led lune 28, 1961. Such materials are sheet-like whereby they occupy a minimum of space in use and storage and may be easily handled, stored and installed. in spite of their very small thickness, they, nevertheless, exhibit a high transmission loss to sound waves because of the fact that they are limp and have a high mass exceeding 'the minimum predetermined value, whereby sound waves impinging on a partition formed of such material do not set up resonant vibrations in the material which, if so vibrated, would in turn re-transmit the sound waves from the opposite side of the partition.

As more fully discussed in the above-identified, copending application, movable sound insulating partitions iind many applications as, for example, in schools, hotels, restaurants and the like. Moreover, as the public becomes accustomed to the desirable qualities of such material not heretofore obtainable, it will, undoubtedly, demand its use in many other applications.

The particular types of sound insulating materials which are described in the above-identified co-pending application utilize woven fabrics in which the mass-providing members are in the form of relatively straight, metallic wires interwoven in the fabric. This construction provides an extremely satisfactory sound insulating material which has a good high transmission loss and which is attractive in appearance. Nevertheless, there are certain applications in which non-fabric types of sound insulating partitions would be more suitable or might, at least, be preferable. Moreover, for economic reasons, it may be desirablevin some instances to manufacture non-fabric types of sound insulating sheet material. For ex Japie, inasmuch as the fabric-type material dictates that if the manufacturer is to produce the fabric-type materials on an economical basis, not only must he have the necessary looms, but he must also be conversant with the textile industry. Consequently, non-textile manufacturers may prefer to make non-fabric materials, and, therefore, an object of the present invention is to provide a new and improved non-fabric sound insulating member.

Another object of the present invention is to provide a sound insulating material having an average transmission loss ot at least the order of 35 decibels and which is suiiciently iiexible that it may be folded or rolled for storage purposes and which is not susceptible to stretching as, for example, by cold flow thereof.

A further object of the present invention is to provide a non-woven sound insulating sheet-like material having an average sound transmission loss of at least the order of 35 decibels.

li,liil,258 Patented Dec. 15, 1964 ICC A still further object of the present invention is to provide a new and improved method of forming a sound insulating material.

Brieiiy, the above and further objects are realized in accordance with the present invention by providing a sheet-like material comprising a plurality of metal linkages which are enclosed within a soft, limp, iller material such, for example, as a flexible foam or sponge vinyl or rubber material, whereby the linkages provide the necessary mass and the soft, tiexible'ller itself or an imperorate skin thereon renders the sound insulating material impervious to air and sui'iiciently limp, so that vibrational waves exerted thereon by impinging sound waves cannot be sustained therein.

Further objects and advantages and a better understanding of the invention may be had by reference 'to the accompanying drawings in which:

FlG. l is a fragmentary plan view of a sound insulating member embodying the present invention, portions thereof being broken away to better indicate the details of construction;

FlG. 2 is a sectional view on an enlarged scale taken along the line 2 2 of FIG. l;

PEG. 3 is a fragmentary plan view of another sound insulating member also embodying the present invention, certain portions thereof being broken away to facilitate a better understanding of the constructional details;

FlG. 4 is a sectional view on an enlarged scale taken along the line i--tl oi FlG. 3;

FIG. 5 is a fragmentary plan view of still another sound insulating member also embodying the present invention, certain portions thereof being broken away to facilitate a better understanding of its construction;

PIG. 6 is a sectional view taken along the line 6--6 of FIG. 5;

FIG. 7 is a fragmentary, perspective view showing two rooms separated by a movable partition embodying a sound insulator of the present invention; and

FlG. 8 is a cross-sectional view showing a preferred method of storing the sound insulating member constituting the movable partition in the installation illustrated in FIG. 7.

The transmission loss, TL., of a material is an index of its sound insulating merit and is equal to the ratio expressed in decibels of the incident sound energy to the transmitted sound energy. The greater the transmission loss of a material the greater is the sound insulation which it provides.

The principal manner in which sound passes through an imperforate member, such as a partition, is by forced vibration of all or part of the partition. Consequently, the entire partition or in some cases small portions thereof, becomes a secondary source of sound waves which radiates sound into the adjoining spaces on the opposite side of the partition. That is to say, the partition functions as a single diaphragm or as multiple diaphragme.

ln accordance with the teachings oi the invention described in the above-identiiied, co-pending application, a sheet-like imperforate partition may be prevented from functioning as such a diaphragm by forming it in such a way and of such material that it is relatively massive and is also limp, i.e., has a Q whose value is negligible.

The Q of a vibrating body is a iisure oi merit having a value indicating the energy loss in the vibrating body,

arenoso used, the sound insulating material forming the partitiony should have a mass in excess of the order of 2.0 pounds per square foot.

Referring now to the drawings and particularly to FlG. 1 thereof, there is shown a portion of a sheet of sound insulating material i@ which comprises a metallic linkage l2 enclosed or embedded in a soft, limp, accid,

'flexible ller material i3, which is encased within a pair of facial skins 14 and l5 which are impervious to air.

The skins ld and l5 are preferably bonded substantially 'throughout their entire inner surface areas to the material 13 exhibiting either an interstitial bond at the interface lfm therebetween (FIG. 2) or a fused body which,

in turn, is so interconnected that the linkage l2 as to be substantially unable to move separately from the linkage 12 either in whole or in part. Accordingly, the skins fill and 15 cannot vibrate or resonate as independent dia- -phragms unless, of course, they carry the massive linkage 'l2 with them. The linkage l2 is selected in accordance with the teachings of the 'above-identified, co-pending application, so as to have a sutiiciently high mass that any `tendency of the skins to oscillate is damped to an extent whereby the transmission loss of the material is greater than that desired for the particular application. For example, a mass in excess of the order of 2.0 pounds per square foot of surface area is required for most purposes where a sound barrier would be employed.

The linkage 12 comprises a plurality of parallel helices 18 joined together by a plurality of straight rods i9 which respectively extend through the turns of two adjacent ones of the helices 1S. The turns or coils of the helices are somewhat flattened, as best seen in FIG. 2, to minimize the thickness of the member lll. As viewed in FIG. l, the helices 18 and the rods 19 extend in a vertical direction whereby the material l@ is flexible about the vertically directed axes of the rods 19, and the material lll, when thus oriented, is suitable for storage in vertically disposed rolls or in vertically disposed pleats, as is commonly used for storage of draperies and cru'tains.

The member l@ must be limp, i.e., have a negligible Q in order to function properly as a sound barrier and, consequently, the filler material 13 should be relatively soft. Moreover, in order to enable facile storage of the member l@ it should be flexible and it has been found that flexible natural or synthetic foam or sponge materials may be satisfactorily used for such purposes. For example, open-'cell styrene, urethane or neoprene foams may be used. Moreover, closed-cell foam or sponge materials may be used as, for exarnp e, vinyl plastisol. Where the filler material l is of the open-cell type, it normally contains passageways extending from one side of the material to the other which, in the absence of the skins lill land 15, would transmit sound waves directly through the material and appreciably decrease the transmission loss thereof. Accordingly, where open-cell filler materials are used, it is necessary to employ the imperfonaite skins 14 and 15 in order for the member lli) to function satisfactorily as a sound barrier. 0n the other hand, even where the closed-cell ller materials are employed it is desirable to provide the skins 14 and l5 in order to provide a material having `a high wear-resistant surface. Most closed-cell materials have a surface which is very susceptible to damage, so that even though a skinless foam sound insulator will operate satisfactorily las a sound insulator, its appearance might soon be marred by normal use and, therefore, the inclusion of the skins ld and l5 is preferable.

Referring to FIG. 3, there is shown a sound insulating member 25 comprising a metal linkage 26 embedded within a soft material 27 which, as best shown in FIG. 4, is encased between a pair of facial skins 29 and 3th which are imperforate and thus impervious to air. Preferably, the skins 29 and are bonded to the material 27 throughout their inner surfaces. The linkage 27 comprises a, plurality of generally helical flattened coils 3l having the turns of adjacent coils interwoven so that the linkage 26 is generally in the form of a conveyor type belt or link chain fence, and when oriented in the position shown in FlG. 3 is flexible about the plurality of vertical axes located at the junetures of the adjacent coils 31. Accordingly, the material 2S is suited for storage in rolls.

The filler material 27 may be the same as that used for the material 13 in the embodiment illustrated in FlG. l. As such it can be vinyl sponge, latex sponge and the like or it might be a solid soft material, such as neoprene. However, it will be understood that solid neoprene is substantially more resilient than are certain vinyls or plastisol Sponges or foams and while such resilience is not sufficiently great as to adversely affect the transmission loss of the material 25, it does produce a material 4which tends to remain in a planar condition and unless held in another position will return of its own accord to the flat, planar state.

Referring now to FIG. 5, there is shown a sound insulating material 35 comprising a metallic linkage 3d embedded in a soft, limp material 37 which, as best seen in FIG. 6, is encased within a pair of facial skins 3d and 39. rl`he linkage 36 comprises a plurality of metallic wires or links 4l which are provided at spaced intervals of about every three to six inches or more with loops 42 which are interlinked with the corresponding loop of the next adjacent o links il whereby there is formed a unitary member which,

when the material .as is oriented in the position shown in FIG. 5, is extremely flexible about the ventical axes of the linkages dl. The member 35 is thus more flexible than either of the materials l@ or 25, assuming that the filler material 37 and the skins 33 and 39 are formed of a comparably flexible material. Moreover, because the linkages dl. are necessarily spaced close together in order to provide the necessary mass to surface area ratio, as is disclosed in the above-identified, co-pending application, the portions of the material 35 between the linkages ll cannot resonate independently of the linkages 41 within the audio frequency range.

ln the embodiments of the present invention illustrated in FiGS. 1-5, inclusive, the mass-providing members are wires which are linked together at relatively closely spaced intervals. This construction has a number of important advantages over an arrangement in which the mass-providing members are separate from one another. Synthetic materials such, for example, as vinyl and other plastics, as we know them today, are extremely susceptible to dimensional changes under conditions which are found where sound insulating curtains are normally used. For example, a sheet of flexible vinyl, ywhen suspended from the ceiling, will stretch in a vertical direction and such stretching is not necessarily uniform throughout the material. Metallic wires perpendicularly of the material, if suitably bonded to the material and extending in a vertical direction, will prevent such stretching, but in order to provide a curtain which is horizontally flexible and which can be rolled from the top, some means, other than vertically disposed wires, must be provided. To this end, wires extending in a generally horizontal direction, but which are interlinked together as disclosed hereinbefore, provide the necessary vertical support throughout the curtain to prevent stretching along the vertical axis and still provide flexibility in a horizontal direction.

Since individual portions of the over-'ill curtain may react as small, independent diaphragms when impingcd upon by sound waves, it is important that the maximum alternas size of all such diaphragms be accurately controlled, and to this end the spacing between the mass providing wires must be accurately controlled, not only in the curtain when irst manufactured but throughout the life of the curtain. If stretching of the curtain were to be permitted, then the size of certain of these diaphragms could increase to the point where the high-frequency transmission loss of the curtain could fall below the acceptable minimum level. The interlocking of the mass-providing members prevents such undesirable condition from occurring.

Referring now to FIG. 7, there is shown a portion of a building which includes a room 50 in the foreground and another room 51 in the background. The rooms S0 and 51 are partially separated by a permanent vertical partition or wall 52 which may include a door (not shown) for permitting passage between the rooms. The wall 52 includes an opening delined by a rectangular frame 54 in which an acoustically opaque partition forming member 55 is suitably supported. When the partition member S5 is shown out of the frame 54, the rooms 50 and 51, are, for most practical purposes, a single room.

The partition member 55 may be formed of any suitable sound insulating materials, such as those illustrated in FIGS. 1 through 6, and may be supported for movement in any direction out of the frame 515. However, it is believed that the insulating members hereinbefore described are best adapted to storage in the form of rolls, as contrasted to storage by pleating. Moreover, it has been found that roll type of storage is best provided in connection with an over-hanging support in which the roll of stored material is supported above the opening to be covered. Accordingly, as shown in FIG. 8, the member 55 is adapted to be stored in a horizontally disposed roll located directly above the frame 55d. As there shown, the member 55 passes through a horizontal slot 57 in the top of the frame 54 and extends over an idler roller 59 to a storage roll 60 connected to a rotatable support or axis 61. Accordingly, in order to withdraw the member 55 out of the frame 54 so as to interconnect the rooms 5t) and 51 the support el is merely rotated in a clockwise direction as viewed in FIG. 8 thereof, thus rolling the member 55 onto the storage roll, which roll is shown partially filled in FIG. 8. ln order to move the member 55 to a room separating position, the member 61 is rotated in a counterclockwise direction, thus unrolling the member 55 and permitting it to fall under the force of gravity across the opening in the frame S4.

The rotation of the axle 61 may be accomplished either by manually operated means or by means of a motor and a suitable drive connection to the member 61. It will be understood that means must be provided for preventing the sound waves from passing around the edges of the member 55 between it and the frame 54 and satisfactory sound traps for accomplishing this are described in my copending applications, Serial No. 84,045, filed January 23, 1961, and Serial No. 90,509 filed February 20, 1961.

Although various types of ller materials and skin materials may be employed in the practice of the present invention, it has been found that a filler of a polymerized flexible vinyl plastisol with a compatible skin of a flexible polymerized vinyl plastisol produces a sound insulating member which is sufliciently flexible for normal applications and, moreover, which has a transmission loss sutliciently high for use as a sound insulating partition.

In order to produce any of the sound insulating members illustrated in FlGS. 1 through 6, the procedure set forth below may be followed in the practice of the present invention:

A conventional mold in the form of a shallow metallic pan or the like is coated with a fluid polymerizable vinyl plastisol of the non-foaming type, c g., not having a blowing agent therein.

The plastisol used to form the skin preferably has a durometer value within the range of from about 40 to 60, although plastisols having other durometer values may be employed, if necessary for a particularly application. The mold is then placed in an oven and heated for a time sutlicient to only partially cure the plastisol which must not be completely cured at this time. An exemplary vinyl plastisol found useful in the practice of the present invention having a durometer value within the range of from about 40 to about 60 may be obtained from Bradley & Vroomans, of Chicago, Illinois.

in the present example, a hot dipped plastisol resin material having a durometer value within the above-mentioned range was obtained from Bradley & Vroomans, and was coated on the mold pan by pouring the same into the pan and rocking the pan until the bottom surface thereof was completely covered. Thus coated with the Bradley & Vroomans plastisol and with the oven preheated to, and maintained at, a temperature of approximately 350 F., the mold was kept therein for approximately eight minutes. At the end of this time the mold was removed from the oven and the now partially cured plastisol was allowed to cool to a temperature of approximately F.

Thereafter, in accord-ance with the practice of the present invention, a filler material comprising a liquid polymerizable vinyl plastisol resin material of the flexible foam or sponge type, including a blowing agent having a durometer value within the range of about l0 to about 60 (obtained from Bradley & Vroomans) and which is compatible with the partially cured plastisol skin material on the mold pan, is supplied to the mold and the metallic linkage then placed in the liquid plastisol ller material. Because of its density the linkage settles to the bottom of the pool of liquid plastisol filler material and rests upon the skin of partially cured plastisol material on the mold. The mold is then returned to the oven which has been preheated to and is maintained at a temperature of approximately 380 F. for a time suicient to complete the cure of both the ller material and the skin. ln curing, the blowing agent causes expansion of the plastisol filler material to form a flexible foam structure, and, in curing of the filler, the metallic linkage is lifted bodily from contact with the lower plastisol layer or skin so that the completed heat reaction product, or formed sound insulating member, the linkage is spaced from the lower skin by a distance determined by the weight of the linkage, its coniiguration, and the particular materials employed to form the sound insulating member. ln the example herein given, a period of approximately twenty-eight (28) minutes at a temperature of approximately 380 F. was found to be suiiicient to completely cure both the aboveidentified ller and skin materials and `to cause the filler and the skin materials to form a single composite sound insulating member with the linkage imbedded therein. lt will be appreciated, of course, that depending upon the physical and chemical characteristics of both the :filler and skin materials, the cured skin and filler may form either a fused mass or may be interstitially bonded at their interface. After curing of the ller and skin materials has been completed, the oven is allowed to cool down to a temperature permitting removal of the mold therefrom. The now formed sound insulating member is 'then removed from the mold.

lt will be noted that in following the above process there is provided a sound insulating member having a skin only on one `side thereof. Where, however, a layer of skin is desired on both surfaces of the plastisol iiller, it is preferable that during the above-described second heating step the mold is removed from the oven before the iiller material has been completely cured. The other outer layer of a flexible plastisol skin of a material cornparable to the material forming the first-mentioned outer skin may then be applied to the exposed surface of the partially cured iiller material by suitable means such as by spraying, brushing and the like. rfhe mold is once ademas more returned to the oven which has been preheated to approximately 380 F. .to complete the curing process. In this manner, both outer skins are either firmly bonded or fused to the filler and the possibility of the skins separating from the iiller is thereby substantially minimized.

lt will be appreciated that in the practice of the present invention the materials used for the skin and for the filler should have compatible chemical and physical characteristics so that, during the curing process, the skin and the ller become rmly bonded or fused, and that .the resulting sound insulating member exhibits a substantially uniform flexibility. It will also be appreciated that where skin and filler materials which have dissimilar chemical or physical characteristics are to be employed it may be found that the skin and ller will be susceptible to separation at the interface thereof. Preferably, the filler material forms a flexible porous or cellular plastisol, foam or sponge in order to provide a sound insulating member having the degree of iiexibility required thereof for handling and which exhibits the necessary high transmission loss. lf desired, a converted vinyl foam or sponge may be used in order to modify the appearance of the completed product.

In the illustrated embodiments of the present invention the plastic portions of the curtains extend over or at least coextensive with the non-stretchable support wires. However, Where feasible, the non-stretchable support Wires may extend beyond the upper edge of the plastic portion of the sheet so as to be directly engageable by the supporting mechanism such, for example, as hangers. Also, the nonstretchable support members also constitute the mass-providing members in the illustrated embodiments of the invention, but it will be understood by those skilled in the art that non-metallic, non-stretchable support members may be used to prevent stretching or other dimensional distortion of the sheet, in which case other mass-providing, high specific gravity material, such as pieces of metal, should be embedded in the plastic carrier.

While the present invention has been described in connection with certain embodiments thereof, it will be understood that those skilled in the art make many changes and modifications without departing from the true spirit and scope of the invention. Therefore, it is intended by the claims which are appended hereto and which form a part of the present specification to cover all such changes and modifications which fall within the true spirit and scope of the present invention.

I claim:

l. A sound insulating member comprising a sheet of limp, flaccid, flexible air-impervious material and a linkage of metallic wires embedded in said sheet, said wires and said sheet having a composite mass of `at least 2.0 pounds per square foot.

2. A sound insulating member comprising a sheet of porous, limp, ilaccid, flexible, air-impervious material and a plurality of metallic Wires embedded in said sheet in closely spaced relationship, the size and number of said wires being selected such that said member has a mass of at east 2.0 pounds per square foot.

3. A sound insulating member as set forth in claim 2 wherein said sheet is formed of a vinyl sponge.

4. A sound insulating member as set forth in claim 3 wherein said metallic wires lie parallel to one another in a substantially common plane and each of said wires is loosely linked with the two adjacent Wires, whereby said member is iiexible along a plurality of taxes parallel to the direction in which said wires extend.

5. A sound insulating member comprising a sheet of limp, flexible material, a generally planar metallic linkage embedded in said sheet and extending substantially cl3-extensive therewith and an imperforate skin overlying at least one face of said shee and having the inner surface thereof bonded to said sheet throughout substantially the entire area thereof.

6. A sound insulating member comprising a sheet of limp, flexible material, a plurality of metallic wires lying in a substantially common piane and extending substantially parallel to one another, and an imperforate skin overlying at least one face of said sheet and having the inner surface thereof bonded to said sheet throughout substantially the entire area thereof.

7. A sound insulating member comprising a sheet of soft, porous flexible material which is pervious to air, a generally planar metallic linkage embedded in said sheet and extending substantially zo-extensive therewith, and first and second imperforate skins respectively overlying the faces of said sheet, said skins being bonded to the adjoining surfaces of .said sheet throughout substantially the entire area thereof.

8. A sound insulating member comprising a sheet of limp, flexible material and a plurality of metallic wires embedded .insaid sheet, said wires lying in substantially the same plane in substantially parallel relationship, each of said wires being provided with loops at spaced intervals interconnecting with loops on the ones of said wires on adjacent sides thereof.

9. A sound insulating member Comprising a limp, flaccid sheet of neoprene, a generally planar metallic linkage embedded in said sheet, said linkage being liexible along a plurality of parallel axes, and said linkage and said sheet having a combined mass of at least 2.0 pounds per square foot.

Vl0. A sound insulating member comprising a sheet of limp, flexible material, a metallic linkage comprising a plurality of interlinked helical coils embedded in said flexible material, said linkage and said sheet having a combined mass of at least 2.0 pounds per square foot.

1l. A sound insulating member comprising a sheet of soft, flexible material having a nonporous surface and a porous body embedding a generally planar metallic linkage comprising a plurality of generally helical coils having the coils on adjacent ones of said helices lying in overlapping relationship, and a plurality of straight metallic rods inter-fitted between the overlapping ones of said coils, whereby to unite said coils into a llexible linkage, said linkage and said sheet having a combined mass of at least 2.0 pounds per square foot.

l2. A method of forming a sound insulating member comprising the steps of: placing a layer of a plastic in a shallow mold, partially curing said plastic, placing a plurality of metallic mass-providing members in said mold over said partially cured plastic7 also placing an uncured plastic material in said mold over said partially cured plastic, and thereafter' curing both plastics to provide a unitary structure in which said metallic members are secured.

13. The method set forth in claim l2 wherein the second plastic material includes a blowing agent whereby the'second plastic material becomes porous during the curing operation.

14. A sound insulating sheet comprising a limp, imperforate, generally planar member, and a plurality of mass-providing members secured to said planar member and uniformly distributed throughout, said mass-providing members being interlocked with one another to prevent dimensional changes in said sheet, said sheet having a mass of at least two (2.0) pounds per square foot.

15. The method of forming a sound insulating memer comprising supplying to a mold a liquid non-foaming polymerizable resin skin matefal which when completely cured forms a flexible body, partially curing said skin material, positioning at least one metal linkage in the mold, supplying to the mold a liquid polymerizable filler material which, when completely cured, forms a flexible body and which is taken from the group consisting of natural and synthetic resins, and curing said skin material to form an outer skin on said filler material when so cured and curinsy said filler material until said linkage is embedded in the cured filler material to thereby form said sound insulating member.

i6. The method of claim i5 wherein said ller mate- E9 rial is taken from the group consisting of flexible, natural, and synthetic foam resins.

17. A sound insulating partition comprising a sheet of limp, flexible material, said material having a distributed mass of at least 2.0 pounds per square foot, said material being subject to stretching, a plurality of vertically disposed, substantially non-stretchable support members embedded in said sheet, and means for supporting said sheet by said support members.

References Cited by the Examiner UNITED STATES PATENTS 259,989 6/ 82 Piekhardt.

283,904 8/83 Laraway. 1,985,487 12/34 Delaney 181-33 2,304,717 12/42 Swart 181-33 1G 2,744,042 5/56 Pace 131-33 2,974,373 3/61 Streed et al. 18-58 2,999,041 9/61 Lappala 181--33 FOREIGN PATENTS 759 1884 Great Britain.

328,982 5/30 Great Britain.

513,580 10/39 Great Britain.

OTHER REFERENCES Architectural Forum (periodical), vol. 111, No. 4, October 1959, page 63, Lead-Filled Fabrics Deaden Sound and Vibration.

15 LEYLAND M. MARTIN, Primary Examiner.

C. W. ROBINSON, LEO SMILOW, Examiners. 

1. A SOUND INSULATING MEMBER COMPRISING A SHEET OF LIMP, FLACCID, FLEXIBLE AIR-IMPREVIOUS MATERIAL AND A LINKAGE OF METALLIC WIRES EMBEDDED IN SAID SHEET, SAID WIRES AND SAID SHEET HAVING A COMPOSITE MASS OF AT LEAST 2.0 POUNDS PER SQUARE FOOT. 